Cross-sectional studies in Northern America, Northern Europe and Asia indicate an increased prevalence and severity of asthma in the obese whereas longitudinal studies have indicated that increasing BMI is associated with increased risk of incident asthma in women. However, the mechanisms through which where-by obesity increases the risk for asthma remain unclear. There are only few studies from North America and Asia that suggested that obesity is associated with increased skin test reactivity and atopic diseases and many more that suggest obesity has no association with atopy. In adult asthmatics, it has also been shown that both medical and surgical weight loss is consistently associated with dramatic improvements in lung function, asthma symptoms, and medication usage. However, in children no study has elaborated on the potential benefits of reducing weight.